Field of the Invention
The present invention relates to a method of manufacturing a solid electrolytic capacitor, and to the solid electrolytic capacitor. More particularly, the present invention relates to a method of manufacturing a solid electrolytic capacitor having a structure that an anode lead terminal is bonded to an anode of a capacitor element by the resistance welding method, and further relates to the solid electrolytic capacitor.
Description of the Related Art
As illustrated in FIG. 6, one type of related-art solid electrolytic capacitor 1 includes a capacitor element 120 including an anode (anode member) 111, a dielectric layer 112 disposed on the anode 111, and a cathode 115 disposed opposite to the anode 111 with the dielectric layer 112 interposed therebetween, an anode lead terminal 131 connected to the anode 111 of the capacitor element 120, and a cathode lead terminal 132 connected to the cathode 115, wherein the solid electrolytic capacitor is entirely encapsulated by an outer coating resin 116 except for respective lead-out portions (exposed portions) 131a and 132a of the anode lead terminal 131 and the cathode lead terminal 132 (see Japanese Unexamined Patent Application Publication No. 2003-124074).
In the solid electrolytic capacitor mentioned above, the cathode 115 includes a conductive polymer layer 113, which is a cathode electrolyte disposed on the dielectric layer 112, and a cathode lead-out layer 114.
The anode lead terminal 131 is connected to a connecting portion (anode lead pin) 111a of the anode 111 by welding, and the cathode lead terminal 132 is connected to the cathode lead-out layer 114 of the cathode 115 by employing a conductive adhesive 133.
Furthermore, in the solid electrolytic capacitor disclosed in Japanese Unexamined Patent Application Publication No. 2003-124074, gold plating layers 141 and 142 are formed on the anode lead terminal 131 and the cathode lead terminal 132, respectively, for the purpose of not only improving and stabilizing solderability with respect to a printed wiring board, but also reducing and stabilizing connection electrical resistance in a portion of the cathode lead terminal 132 where the cathode lead terminal 132 is connected to the capacitor element (electrical component element) 120 through the conductive adhesive 133.
In the solid electrolytic capacitor having the above-described structure disclosed in Japanese Unexamined Patent Application Publication No. 2003-124074, however, when trying to weld the connecting portion (anode lead pin) 111a of the anode 111 and the anode lead terminal 131 to each other by the resistance welding method that is widely used as a general technique, if contact resistance between the anode and the anode lead terminal is low, sufficient heating would not be obtained, and a difficulty would be caused in reliably bonding the anode lead terminal and the anode to each other. This may lead to the problem that the anode lead terminal and the anode are not bonded to each other in some cases (i.e., a bonding failure), or that the anode lead terminal may be dropped (peeled) from the anode due to insufficient bonding strength during a later manufacturing step or during actual use as a product.
In the embodiment disclosed in Japanese Unexamined Patent Application Publication No. 2003-124074, the gold plating layer is formed on the anode lead terminal. Therefore, the contact resistance between the anode and the anode lead terminal tends to lower, and the above-mentioned problem is more apt to occur.
It is conceivable to increase energy during the resistance welding (i.e., welding power) in order to reduce the above-mentioned troubles, such as the failure of bonding between the anode lead terminal and the anode, and the dropping (peeling) of the anode lead terminal during the manufacturing step or the actual use. However, if the energy during the resistance welding is too large, another problem arises in that an incidence of the so-called splash failure, i.e., scattering of metal to the surroundings, increases.